Deuteron NMR spectra of ND4ClO4 single crystal at low temperatures

: Birczynski A, Lalowicz ZT, Ingman LP, Punkkinen M, Ylinen EE

Publisher: ACADEMIC PRESS INC ELSEVIER SCIENCE

: 1993

Solid State Nuclear Magnetic Resonance

SOLID STATE NUCLEAR MAGNETIC RESONANCE

: SOLID STATE NUCL MAG

: 1

: 6

: 329

: 344

: 16

: 0926-2040

DOI: https://doi.org/10.1016/0926-2040(93)90015-F

H-2 NMR spectra of ND4ClO4 single crystal were obtained at v(0) = 44 MHz. Orientation and temperature (1.9-75 K) dependences were measured. Fitting the spectra gives the effective quadrupole coupling constants for all deuterons and the ground torsional level structure. The isotope reduction of the (A-T) and (A-E) tunnelling splittings, i.e., the ratios of the respective splittings for NH4+ and ND4+, were found to be different. The splittings at T = 24 K are about 60% of the helium temperature values. The spectrum undergoes intermediate narrowing by reorientations between 26 and 34 K and tunnelling related features in the spectra are eradicated. After reaching the extreme narrowing limit, a doublet with gradually decreasing separation was observed, what was attributed to averaging by torsional oscillations of increasing amplitude. At high temperatures (T > 75 K), the narrow spectrum reflects fast multiaxial reorientation of the ammonium ion.

Physical sciences